The objective of this research is to explore the possibility of chronic microstimulation of the spinal cord. If successful, such a technique could be part of a prosthesis to restore genito-urinary, bowel and other motor functions to victims of spinal cord injury. Information from spinal cord microstimulation studies is especially needed by designers of neural prostheses for paraplegic individuals who have sustained injuries to their spinal cords above the lumbosacral region. In particular, it may be possible to selectively excite neurons innervating the bladder detrusor muscle while simultaneously stimulating interneurons which have inhibitory synaptic connections with neurons innervating the external urethral sphincter. Likewise, discrete control of penile erection, ejaculation, bowel evacuation and control of the somatic musculature of the limbs may be possible by selective spinal cord microstimulation below the level of spinal cord injury. Before microstimulation of the spinal cord can be evaluated in humans, a suitable chronic stimulating microelectrode must be developed and its safety and effectiveness demonstrated in animals. Contract supported research over the past five years has demonstrated that it is possible to insert, stimulate and maintain discrete wire microelectodes in the sacral spinal cord on a chronic basis without undue tissue damage. However, the present design of the microelectrode/lead wire system causes excessive mechanical damage during movement of the spinal cord within the spinal canal and must be improved. This new research project will complete the establishment of safe ranges of stimulation parameters and will investigate the use of thin film, integrated circuit microelectrodes in the lumbosacral spinal cord.